Tropical Depression Irma Forecast Discussion

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Tropical Depression Irma Discussion Number 52
NWS National Hurricane Center Miami FL AL112017
1100 PM EDT Mon Sep 11 2017
Irma continues to move farther inland and is approaching the
Georgia-Alabama border, with a large rain shield spread across much
of the southeastern United States. There have been no surface
reports of sustained tropical-storm-force winds from within the
tropical storm warning areas, so it is assumed that Irma has
weakened to a tropical depression with maximum winds of 30 kt.
Winds should continue to decrease over the next day or so while
Irma remains over land and is hammered by 40 kt of shear. These
conditions should also cause the deep convection to die off, and
Irma is likely to become a remnant low in about 24 hours. The
global models are then in agreement that the remnant low will
dissipate by 48 hours.
Irma has turned northwestward with an initial motion of 325/14 kt.
The depression is embedded within a larger cyclonic gyre, which is
expected to move northwestward through Monday, and then turn
north-northwestward over western Tennessee or western Kentucky
before it dissipates.
Water levels have fallen below the storm surge warning criteria
along the southeastern United States coast and the Florida west
coast. The Storm Surge Warnings in those areas have therefore been
discontinued.
Future information on this system can be found in Public
Advisories issued by the Weather Prediction Center beginning at
5 AM EDT, under AWIPS header TCPAT1, WMO header WTNT31 KWNH, and on
the web at http://www.wpc.ncep.noaa.gov.
KEY MESSAGES:
1. Irma continues to produce very heavy rain across the
southeastern United States. Intense rainfall rates are leading to
flash flooding and rapid rises on creeks, streams, and rivers.
Significant river flooding will persist over the Florida peninsula
in the wake of Irma and across Georgia, South Carolina and
north-central Alabama where additional heavy rains are expected.
Portions of these states within the southern Appalachians will be
especially vulnerable to flash flooding. Irma is also expected to
produce heavy rains in northern Mississippi and southern portions of
Tennessee and North Carolina, where local flooding may occur.
2. Storm surge flooding is subsiding along portions of the coasts of
western Florida, Georgia, and South Carolina.
FORECAST POSITIONS AND MAX WINDS
INIT 12/0300Z 32.4N 84.9W 30 KT 35 MPH...INLAND
12H 12/1200Z 33.8N 86.4W 25 KT 30 MPH...INLAND
24H 13/0000Z 35.2N 88.2W 25 KT 30 MPH...POST-TROP/INLAND
36H 13/1200Z 36.4N 88.6W 20 KT 25 MPH...POST-TROP/INLAND
48H 14/0000Z...DISSIPATED
$$
Forecaster Berg
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